Limited backflow reflux valve and method

ABSTRACT

A limited backflow reflux valve for connection between a syringe, catheter, and bulk container of injection fluid. The reflux valve permits injection of fluid from the syringe through the catheter into the patient, and also permits refilling of the syringe from the bulk container, without disconnection of any tubing. The reflux valve also permits a limited volume of fluid to backflow from the catheter into the syringe, so that the catheter may be checked for patency, but prevents any further backflow along this path after this limited volume. Therefore, the limited backflow reflux valve not only permits injection through the catheter, but also permits both withdrawal of blood from the patient and refilling of the syringe from the bulk contrast media container, without requiring disconnection of the catheter or other tubing and without risk of contamination of the syringe or introduction of air, increasing the efficiency of the injection process, enhancing safety, and reducing waste of injection fluid.

This is a division of application Ser. No. 08/535,771 filed on Sep. 28,1995, now U.S. Pat. No. 5,665,074 entitled LIMITED BACKFLOW REFLUXVALVE.

FIELD OF THE INVENTION

The present invention relates to valve mechanisms for injection of fluidinto animals through a catheter.

BACKGROUND OF THE INVENTION

In many medical environments, a medical fluid is injected into a patientduring diagnosis or treatment. One example is the injection of contrastmedia into a patient to improve CT, Angiographic, Magnetic Resonance orUltrasound imaging, using a powered, automatic injector. The contrastmedia used in these applications is typically expensive and therefore ispreferably conserved to the extent possible.

During injections of this kind, it is typical for the injector operatorto first mount a syringe to the injector and fill the syringe withcontrast media from a separate bulk contrast media container. Then, oneend of a translucent tube is coupled to the syringe, and the other endof the tube is connected to a needle or catheter and inserted into thepatient, permitting subsequent injection of contrast media into thepatient.

Often, during the procedure, the operator briefly withdraws blood fromthe patient into the catheter to check for patency of the catheter, byrunning the injector backward to withdraw blood from the catheter orneedle and into the translucent tube. If blood is visible in thecatheter after this brief withdrawal, the operator can confirm that theneedle or catheter is not obstructed, for example by blood clots.Thereafter, the operator proceeds with the injection, by running theinjector forward to force contrast media from the syringe into thepatient.

In angiographic applications, often small injections of contrast mediaare made during final positioning of the catheter, in order to visualizethe vasculature of the patient and position the catheter in relation tothat vasculature. (Small contrast media injections are necessary becausethe catheter is not visible under fluoroscopy.)

One difficulty with the procedures described above is the need todecide, early in the process, the amount of contrast media to place inthe syringe. For safety reasons, any contrast media remaining in thesyringe after an injection cannot be reused on another patient.Therefore, due to the cost of contrast media, it is desirable to fillthe syringe with only the amount of contrast media that is needed forthe injection. Unfortunately, this amount is difficult to predictaccurately. Overestimation of the needed amount results in wastedcontrast media. Underestimation requires that the syringe be refilled;this involves disconnecting the syringe from the tube, connecting thesyringe to the bulk contrast media container, withdrawing additionalcontrast media into the syringe, and then reconnecting the syringe tothe tube. This refilling operation is not only tedious, but it alsocreates safety hazards due to the possible introduction of air into thecatheter during disconnection and re-connection, and possible exposureof the operator and/or contamination of the bulk container by contrastmedia in the syringe which has potentially been exposed to the patient'sblood.

Another difficulty arises during catheter positioning, when making smallinjections of contrast media to aid in visualizing the vasculature ofthe patient. To preserve sterility, the physician typically does notdirectly operate the power injector, but must orally communicatecommands to the injector operator; this can be difficult to coordinatebecause the physician is simultaneously manipulating the catheter andwatching the fluoroscope. Furthermore, some power injectors forinjecting contrast media are designed for high flow rate injections andcannot be precisely controlled for small volume injections. As a result,when using these injectors often more contrast than necessary may beconsumed during catheter positioning.

SUMMARY OF THE INVENTION

In accordance with the invention, these difficulties in using andrefilling a contrast media injector and syringe are avoided by includinga limited backflow reflux valve between the syringe, tubing, and bulkcontainer of injection fluid. This valve includes one inlet port, oneoutlet port, and a third, bi-directional port. A first check valvepermits fluid flow only from the inlet port to the bi-directional port,and a second check valve permits fluid flow from the bi-directional portto the outlet port.

The inventive reflux valve is connected between a syringe, catheter, andbulk container of fluid, by attaching the bulk contrast media containerto the inlet port, the catheter to the outlet port, and the syringe tothe bi-directional port. Thus, the reflux valve permits injection offluid into the patient from the syringe and refilling of the syringefrom the bulk container, without disconnection of any tubing and withoutrisk of contamination of the bulk contrast media container.

The inventive reflux valve also permits the withdrawal step describedabove; specifically, the second check valve between the bi-directionaland outlet ports is a limited backflow check valve which permits alimited volume of fluid to backflow into the outlet port, but preventsany further backflow into the outlet port after this limited volume.This limited volume is sufficient to permit blood to become visible inthe tubing during withdrawal from the patient.

A limited backflow reflux valve in accordance with the invention, whenused in contrast media injection, permits both withdrawal of blood fromthe patient and refilling of the syringe from the bulk contrast mediacontainer, without requiring disconnection of the catheter from thepatient and without risk of contamination of the syringe or bulkcontainer, or introduction of air. This increases the efficiency of theinjection process and also enhances its safety. Furthermore, because thesyringe can be refilled by simply running the injector backward towithdraw fluid, through the limited backflow reflux valve, from the bulkcontrast media container, the operator is less likely to intentionallyoverestimate the amount of contrast media needed for an injection, thusreducing waste of contrast media.

In various specific embodiments of the invention, the limited backflowcheck valve is a piston fitted in a cylinder for translation through thecylinder during forward and reverse injection of fluid. One end of thecylinder carries the inlet port and bi-directional port, and theopposite end cylinder carries the outlet port.

In one specific embodiment, the circumferential boundary of the pistonis cupped to permit fluid flow around the piston and out through theoutlet port, but prevent fluid flow around the piston into the refluxvalve through the outlet port. In a specific enhancement of thisembodiment, the reflux valve includes a hand-actuatable plunger,attached to the piston of the limited backflow check valve, andextending outside of the cylinder. This hand-actuatable plunger may beused to move the piston by hand and thereby manually pump small amountsof contrast media into the patient to assist in positioning thecatheter. Since the reflux valve is sterile, the plunger can bemanipulated by the physician to manually inject contrast media into thepatient during catheter positioning, simplifying this procedure and alsoenabling the physician to inject precisely controlled volumes ofcontrast media (equal to the displacement of the piston in thecylinder).

The hand-actuatable plunger may be locked in placed by a suitablelocking mechanism, so that the motion of the piston can be limitedduring power injection using the reflux valve. One specificallydisclosed locking mechanism includes teeth molded into the plunger whichmate with a single tooth on a movable locking member. By engaging thislocking member, movement of the plunger can be prevented or limited to asmall range so as to prevent or limit the amount withdrawn through theoutlet port.

In an alternative embodiment, the cylinder is enlarged at the endadjacent the outlet port, permitting fluid flow around the piston whenthe piston is at this end of the cylinder. At any other position in thecylinder, the piston seals against the walls of the cylinder, preventingfluid flow around the piston. An elastic member produces spring tensiontending to draw the piston out of the enlarged region of the cylinder,thus ensuring a seal whenever pressure is equalized and fluid is notflowing around the piston.

In either of these embodiments, the housing may include ribs whichextend from the end of the housing adjacent the outlet port, and engagethe piston to prevent the piston from translating fully to this end ofthe cylindrical housing, ensuring free flow of fluid around the pistonwhile the piston is at this end of the housing.

In yet another specific embodiment of the invention, the limitedbackflow reflux valve includes a gate mounted for rotation within thereflux valve housing. The gate rotates in a first direction to permitunlimited fluid flow out of the housing through the outlet port, and inan opposite direction through a limited angle to permit a limited volumeof fluid flow into the housing through the outlet port. A spring memberurges the gate to a predetermined angular position within the housing toseal the second check valve in the absence of fluid flow out of theoutlet port.

Other aspects of the invention include a complete powered fluidinjection system including a powered injector, a bulk container offluid, and a catheter coupled through the above-described limitedbackflow reflux valve.

Another aspect is a contrast media delivery system in which a bulkcontainer of contrast is coupled to a limited backflow reflux valve suchas described above.

An additional aspect is the above-described methods for injecting fluidinto a patient using the limited backflow reflux valve.

The above and other aspects, objects and advantages of the presentinvention shall be made apparent from the accompanying drawings and thedescription thereof.

BRIEF DESCRIPTION OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, andthe detailed description of the embodiments given below, serve toexplain the principles of the invention.

FIG. 1A is a partial cross-sectional View of a limited backflow refluxvalve including a plunger and plunger lock in accordance with principlesof the present invention, shown with the plunger and piston at theirrearwardmost positions.

FIG. 1B is a view of the limited backflow reflux valve of FIG. 1A shownwith the plunger and piston at their forwardmost positions.

FIG. 1C is a partial view of an alternative embodiment of teeth 35 and35a.

FIG. 1D is a cross-sectional view of the valve of FIG. 1A taken on lines1D--1D.

FIG. 2A is a cross-sectional view of a second embodiment of a limitedbackflow reflux valve in accordance with principles of the presentinvention, shown with the piston at its rearwardmost position.

FIG. 2B is a view of the limited backflow reflux valve of FIG. 2A shownwith the piston at its forwardmost position.

FIG. 2C is a cross-sectional view of the valve of FIG. 2A taken on lines2C--2C.

FIG. 3A is a schematic isometric view of a third embodiment of a limitedbackflow check valve in accordance with principles of the presentinvention, shown with the gate at its rearwardmost position.

FIGS. 3B is a schematic views of the limited backflow check valve ofFIG. 3A shown with the gate at the position achieved in the absence offluid flow, and FIG. 3C is a schematic view of this valve shown with thegate at the position achieved during forward fluid flow.

FIG. 3D is an elevation view of the axle and spring assembly of thevalve of FIGS. 3A-3D.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring to FIGS. 1A, 1B, 1C and 1D, a limited backflow reflux valve 10in accordance with principles of the present invention includes threeports for fluid flow into and out of the valve 10. Outlet port 12includes a standard luer fitting sized for connection to the tubingleading to a catheter (not shown). Inlet port 16 is sized for connectionto a syringe of a power injector of the type used to inject fluid intothe patient. Bi-directional port 14 is sized for connection to a bulkcontainer of contrast media via suitable tubing.

Valve 10 includes a main cylindrical housing section 18, and a secondcylindrical housing section 20 having a smaller diameter than mainhousing section 18. A piston 22 is seated in main housing section 18 andmay slide transversely through this section as shown in FIG. 1A incomparison to FIG. 1B. Piston 22 is mounted to a plunger 26 by insertionof an extension 27 at the rear of piston 22 into a recess 28 in plunger26. Seated between piston 22 and plunger 26 is a sealing ring 24 whichencircles the outer edge of piston 22 and engages the circular innerwall 29 of housing section 18 to form a fluid seal therewith.

Sealing ring 24 is manufactured of a resilient material such as rubberand is cupped at its peripheral rim; accordingly, under fluid pressurering 24 will resiliently yield to permit fluid to flow from the rearside of ring 24 (the side from which plunger 26 extends) to the forwardside of ring 24 (the side having the body of piston 22). However, iffluid pressure is removed or reversed, sealing ring 24 will re-engagethe cylindrical wall 29 of section 18 and will form a fluid-tight sealpreventing fluid flow in the opposite direction from the forward side ofring 24 to the rearward side of ring 24. Thus, ring 24, interacting withthe cylindrical wall 29 of housing section 18, forms a check valvepermitting forward fluid flow toward outlet port 12 but preventingreverse fluid flow.

Plunger 26 extends rearwardly through housing section 20, emerges fromhousing section 20, and terminates in a thumb grip 30. Centrally locatedalong the length of plunger 26 is a pair of sealing rings 32 whichengages the inner surface 31 of housing section 20 to form a sealtherewith and prevent fluid from escaping from housing section 20.Housing section 20 has, on its outer sides, finger grips 34. Grips 30and 34 are sized and positioned so that a physician's fingers may beplaced in grips 34 and the thumb from the same hand placed in grip 30,so that plunger 26 may be manually driven into or retracted from housingsections 18 and 20.

The exterior surface of plunger 26, rearward of sealing rings 32,carries a number ofteeth 35, which extend from plunger 26 along asubstantial portion of the length of plunger 26. However, a rearwardmostauto-extravasation zone 33 of plunger 26 does not bear any teeth, forreasons that will be noted below.

At the rearward end of housing section 20, a twist-lock 37 is journalledto a flange 38 on housing section 20. Twist-lock 37 carries one or moreteeth 35a (one being shown in the Figs.) which can be rotated such thatthe tooth or teeth on twist-lock 37 mate to and engage the teeth 35 onplunger 26. Accordingly, by rotating twist-lock 37, plunger 26 may belocked in a given axial location or left free to slide axially withinhousing section 20. A torsion spring 37a may be included in thejournalled connection between twist-lock 37 and housing section 20,producing a force tending to rotate twist-lock 37 into engagement withteeth 35 on plunger 26 and thereby lock plunger 26 in place. In oneembodiment of the invention, a snap-fitting (not shown) may be includedin the twist-lock 37 to permit the twist-lock 37 to be rotated and heldin its unlocked position against the force of the torsion spring 37a.

In the embodiment shown in FIG. 1C, teeth 35 and 35a are barbed, suchthat twist-lock 37 will not prevent forward motion of plunger 26 withinthe housing of syringe 10, but will prevent rearward motion of plunger26 within the housing.

The various uses and advantages of these different twist-lockembodiments will be noted below.

Inlet port 16 is in fluid communication with the interior of housingsections 18 and 20 through a check valve barrel 36. Barrel 36communicates with tie interior of housing section 20 at a position whichis always forward of sealing rings 32 even when piston 22 and plunger 26are at their forwardmost positions (FIG. 1B). This position is alsoalways rearward of sealing ring 24 even when piston is at itsrearwardmost position (FIG. 1A).

A check valve ball 39 is positioned inside of barrel 36. A spring 40 iscompressed inside barrel 36 with ball 39 to produce a positive forceurging ball 39 toward the outer wall 41 of barrel 36. Barrel 36, ball 39and spring 40 cooperate to form a check valve which permits fluid flowthrough inlet port 16 into the housing of valve 10 but prevents fluidflow through inlet port out of the housing of valve 10.

Bi-directional port 14 is also in fluid communication with the interiorof housing section 20 via a channel 42. Channel 42 communicates withhousing section 20 at a position opposite to barrel 36, i.e., at aposition which is always forward of sealing rings 32 even when piston 22and plunger 26 are at their forwardmost position (FIG. 1B) and which isalways rearward of sealing ring 24 even when piston 22 is at itsrearwardmost position (FIG. 1A).

Housing section 18 terminates, at its forward end, in a conical end cap44 having a shape which is congruent to the conical piston 22.Positioned within end cap 44 are spacer ribs 46 which project inwardlyfrom the conical surfaces of end cap 44. Four such ribs 46 are shown inFIG. 1D although fewer or more ribs could be included. When piston 22advances to its forwardmost position as shown in FIG. 1B, the conicalfront surface of piston 22 rests against ribs 46, leaving acircumferential gap between the conical front surface of piston 22 andthe conical interior surface of end cap 44 through which fluid may flowinto outlet port 12.

Housing section 18 terminates, at its rearward end, in a second conicalend cap 48 which mates with a conical surface on plunger 26. Unlike theinterior surface of end cap 44, the interior surface of end cap 48 doesnot carry ribs or spacers, so that when the plunger is translated to itsfully-rearward position, the conical surface of plunger 26 may matefully with the conical interior surface of end cap 48 to form afluid-tight connection.

The above-described limited backflow reflux valve 10 may be used in anumber of different ways to perform an injection procedure, some ofwhich are described below for exemplary purposes. These procedures willbe described with reference to the injection of contrast media into ananimal patient for the purpose of improving CT, Angiographic, MagneticResonance or Ultrasound imaging. Due to the cost of contrast media, theadvantages of the invention are particularly dramatic in suchinjections; however, numerous other similar injection procedures couldbe performed using the above-described valve 10 with like effects.

In the injection procedure, a first step is to fill the syringe on thepower injector with contrast media for the injection. This step isperformed by coupling a bulk container of contrast media (such as a bag,cup, or bottle) to inlet port 16, and coupling the syringe tobi-directional port 14. Then, the power injector is run in reverse towithdraw air and fluid into the syringe. This reduces the pressureinside of housing section 18 and 20 in the region forward of sealingrings 32 and rearward of sealing ring 24. The cupped shape of sealingring 24 causes sealing ring 24 to maintain a tight seal against housingsection 18, preventing air from passing sealing ring 24.

If the frictional force of sealing ring 24 is sufficiently small, theinitial pressure drop produced by reverse operation of the powerinjector will cause piston 22 and plunger 26 to move rearwardly throughhousing sections 18 and 22 toward the position shown in FIG. 1A. Piston22 and plunger 26 will Be driven in this direction due to the lowercross-sectional area of housing section 20 as compared to housingsection 18. This force will continue to act until piston 22 and plunger26 have translated to their fully rearward position shown in FIG. 1A, atwhich time piston 22 and plunger 26 will cease motion.

Further pressure reduction caused by continued reverse operation of thepower injector will overcome the compression force produced by spring40, and cause ball 39 to withdraw from the outer end of check valvebarrel 36, allowing air and fluid to flow from the bulk contrast mediacontainer into inlet port 16, through the housing of valve 10, and outof bi-directional port 14 into the syringe. Thereafter, continuedreverse operation of the power injector will cause contrast media fromthe bulk container to fill the power injector syringe.

It should be noted that if the motion of piston 22 and plunger 26 areimpeded, either by high friction between sealing ring 24 and housingsection 18, or because twist-lock 37 has been rotated to engage withteeth 35 on plunger 26, then piston 22 and plunger 26 will not movebefore air and fluid are admitted into valve 10 through inlet port 16.However, sealing ring 24 is configured for low-friction operation sothat plunger 26 will be drawn rearwardly prior to the introduction offluid through inlet port 16. Furthermore, before filling the syringethrough valve 10, plunger 26 should be retracted to its rearwardmostposition, or alternatively twist-lock 37 should be rotated and snappedor manually held in its disengaged position, so that piston 22 andplunger 26 will translate to the position shown in FIG. 1A prior to theintroduction of fluid through inlet port 16.

In one embodiment, valve 10 is supplied from the manufacturer withplunger 26 already in its fully-rearward position. In this case, it isunnecessary to move plunger 26 to its rearwardmost position or to snapor manually hold twist-lock 37 in its disengaged position during initialfilling through valve 10. (Since valve 10 comes in contact with bloodfrom the patient, it must be disposed after use; therefore, the valve 10will only be used for one refilling procedure, and so if valve 10 issupplied with plunger 26 in its fully rearward position, the plunger 26will be in this position during initial filling.)

As a final aside, it should be noted that if barbed teeth (FIG. 1C) areused, and valve 10 is supplied from the manufacturer with plunger 26 inits rearwardmost position, the valve 10 need not be provided with a snapfor holding twist-lock 37 in its disengaged position, since in such acase all procedures requiring disengagement of twist-lock 37 areperformed manually, and in such cases twist-lock 37 can be easilymanually disengaged by hand in a manner described below.

When the desired amount of contrast media has been drawn through valve10 and into the syringe, the backward motion of the power injector isterminated. At this instant, the pressure inside of valve 10 isequalized, and as a result the compression force of spring 40 forcesball 39 to engage to the outward end of check valve barrel 36, sealinginlet port 16 from the interior of valve 10.

After thus filling the power injector syringe, a length of high pressuretubing, for connection to the catheter, is attached to the outlet port12 of valve 10. The power injector is then run forward to force any airin the syringe into valve 10 and out through the high pressure tubing.During this operation the power injector is typically tilted upwards sothat any air in the power injector syringe moves to the nozzle of thesyringe. Furthermore it is preferred that valve 10 be tilted upward sothat outlet port 12 is elevated relative to the remainder of valve 10 sothat gravity causes any air bubbles entrained in valve 10 to move to andout of outlet port 12.

As the power injector forces air and contrast media into valve 10through port 14, a positive pressure is produced inside of housingsections 18 and 20 in the region forward of sealing rings 32 andrearward of sealing ring 24. This positive pressure tends to increasethe sealing pressure on ball 39 enhancing the seal at inlet port 16.Furthermore, due to the different cross-sectional areas of housingsections 18 and 20, this positive pressure generates a forward forceupon piston 22 and plunger 26 urging piston forwardly toward theposition shown in FIG. 1B. The outward resilient force of the cuppedouter perimeter of sealing ring 24 is sufficiently large that thispositive pressure differential will cause piston 22 and plunger 26 tomove forwardly to the position shown in FIG. 1B, provided twist-lock 37does not prevent such motion.

For reasons noted below, it is desirable for the piston 22 and plunger26 to move to the forwardmost position shown in FIG. 1B by the end ofthe setup procedure and before injecting fluid. Accordingly, the outwardresilient force of the cupped outer perimeter of sealing ring 24 issufficiently large that piston 22 will move forward if not impeded bytwist-lock 37. If barbed teeth (see FIG. 1C) are used on twist-lock 37,then plunger 26 will freely translate in the forward directionregardless of whether twist-lock 37 is disengaged. However, if the teeth35 and 35a are not barbed (see FIGS. 1A and 1B), then twist-lock 37should be held open during initial bubble removal to permit plunger 26to move to its forwardmost position.

After piston 22 and plunger 26 reach their forwardmost positions shownin FIG. 1B, further forward motion of the power injector increasespressure inside of valve 10, ultimately overcoming the resilient forceproduced by sealing ring 24 and permitting air and contrast media toflow around piston 22 and into conical end cap 44 and out of outlet port12 into the tubing connected thereto.

After sufficient forward motion of the power injector, all air in thesyringe, valve 10 and tubing can be expelled, so that the system isprepared for use in injection. Accordingly, the tubing at outlet port 12may be connected to the catheter and the catheter inserted into thepatient.

As noted above, in some injection procedures, it is desirable to injecta small amount of contrast media to aid in visualizing the vasculatureof the patient and positioning the catheter. To permit this operation,twist-lock 37 is disengaged to permit free movement of plunger 26 andpiston 22. Then, to perform a small-volume injection, the physician ortechnician grasps valve 10 with his/her thumb and two fingers usinggrips 30 and 34, and manually moves plunger 26 and piston 22 rearwardlyand forwardly to pump small amounts of contrast media through thecatheter and into the patient. For this operation, twist-lock 37 must bedisengaged, which can be done by rotating twist-lock 37 with a thirdfinger on the same hand used to grasp grips 30 and 34.

When piston 22 is manually urged rearwardly, a positive pressure isdeveloped inside the housing of valve 10 in the region rearward ofsealing ring 24. When this pressure reaches a sufficient level, itovercomes the resilient force produced by the cupped exterior of sealingring 24, permitting contrast media to flow around piston 22 from therearward side of sealing ring 24 to the front side of sealing ring 24.Thereafter, when piston 22 is manually urged forwardly, a positivepressure is developed inside of valve 10 in the region forward ofsealing ring 24. This positive pressure enhances the seal of sealingring 24, such that no fluid may flow around sealing ring 24.Accordingly, when the pressure reaches a level greater than thepatient's blood pressure, contrast media is injected from the portion ofvalve 10 forward of sealing ring 24 into the patient through thecatheter. At the same time, as piston 22 moves forward, a negativepressure is developed in the portion of valve 10 rearward of sealingring 24. This negative pressure eventually overcomes the compressionforce of spring 40, such that additional contrast media is supplied tovalve 10 through inlet port 16.

Through the above interactions, contrast media may be injected into thepatient in small, measured quantities by repeated forward and reversemotion of plunger 26.

After the catheter has been properly positioned, a large-scale injectionof contrast media may be performed by activating the power injector.Doing so will cause contrast media to flow into valve 10 throughbi-directional port 14, initially translating piston 22 to itsforwardmost position (if twist-lock 37 is disengaged or has barbedteeth) and thereafter forcing fluid flow around sealing ring 24. (Oncesealing ring 24 has been deflected by forward flow of fluid throughvalve 10, the cross-sectional area of the gap between sealing ring 24and the interior of housing section 18 is larger than thecross-sectional area of the syringe nozzle and tubing; therefore, valve10 does not produce any substantial resistance to fluid flow at evenhigh flow rates.)

As noted below, it may be desirable for plunger 26 to be placed in itsfully-forward position during an injection procedure. If barbed teethare used, such positioning will be automatically achieved from thenatural motion of plunger 26 in response to fluid pressures in the valve10. However, if barbed teeth are note used, plunger 26 must be manuallymoved to its fully-forward position, or twist-lock 37 must be disengagedduring injection so that plunger 26 naturally moves forward in responseto fluid pressures in the valve 10.

It may be desirable to position plunger 26 at its fully-forward positionbecause, at any time during the injection procedure, the physician maywish to withdrawn blood through the catheter and into the tubing tocheck for patency of the catheter. To do so, the physician operates thepower injector in reverse, producing a negative pressure inside of thesyringe. If piston 22 and plunger 26 are at their forwardmost position,they will respond to this negative pressure by moving rearwardly (in thesame manner as discussed above with respect to initial filling of thesyringe), drawing blood out of the patient and into the catheter. Whenblood becomes visible in the tubing, it can be confirmed that thecatheter is not blocked.

During this withdraw procedure, twist-lock 37 should be in position toengage with the teeth 35 on plunger 26. However, since there are noteeth in the auto-withdrawal zone 33 of the plunger 26, if plunger 26 isfully forward at the beginning of withdrawal twist-lock 37 will beunable to engage plunger 26, and plunger 26 will be able to moverearwardly out of the housing of valve 10 for a distance equal to thelength of the auto-withdrawal zone. Thereafter, twist-lock 37 willengage teeth 35 in plunger 26 and prevent further movement. Thus, ifplunger 26 is in its forwardmost position during injection, acontrolled, limited volume of blood can be withdrawn from the patientbefore engagement of the twist-lock 37. Thereafter, twist-lock 37 willengage the teeth on plunger 26 and prevent further withdrawal so thatfurther rearward motion of the power injector will not withdraw blood,but rather will draw fluid into valve 10 through inlet port 16 in themanner discussed above with respect to filling the syringe.

Thus, the twist-lock 37, interacting with plunger 26, causes apredetermined quantity of fluid (e.g., 2 ml) to be withdrawn from thepatient by operation of the power injector, without the need for highlyaccurate operation of the power injector. This predetermined quantitycan be selected to be less than the total volume of the tubing andcatheter, such that blood is unable to reach valve 10, preventingcontamination. However, even if blood is allowed to reach valve 10,because sealing ring 24 is tightly sealed to the interior of housingsection 18 during withdrawal any blood withdrawn from the patient intovalve 10 is contained within valve 10 in the region forward of sealingring 24, avoiding contamination of either the power injector syringeconnected to port 14 or the bulk contrast media container connected toport 16.

For reference, a typical small catheter for a non-angiographic procedureis about 3 inches long and 0.02 inches inside diameter, resulting in avolume of 0.015 ml captured in the catheter. A typical small catheterfor an angiographic procedure is about 10 inches long and 0.03 inchesinside diameter, resulting in a volume of 0.116 ml captured in thecatheter. A typical large catheter (for angiographg) is 40 inches longand 0.05 inches inside diameter, resulting a volume of 1.287 ml capturedin the catheter. Thus, for these typical sizes, an withdrawal of 2 ml ofblood from the patient would be sufficient for blood to appear in thetubing leading to the catheter.

At any time during an injection, it may be discovered that there isinsufficient contrast media remaining in the syringe to complete theprocedure. In such a case, the technician need only operate the syringein reverse, which (possibly after initial withdrawal of a limited volumeof blood into the catheter) will cause additional contrast media to flowfrom the bulk container through inlet port 16 and refill the syringe.Thus, the syringe may be refilled at any time during the procedure,without disconnecting tubing and without risk of contamination ofintroduction of air.

Referring now to FIGS. 2A and 2B, a simplified embodiment of a limitedbackflow reflux valve operates generally under the principlesillustrated above, but without certain features. Specifically, thesimplified valve 100 includes, as before, an outlet port 12 forconnection to tubing leading to a catheter, a bi-directional port 14 forconnection to a syringe, and an inlet port 16 for connection to a bulkcontainer of injection fluid.

As in the embodiment of FIGS. 1A-1D, inlet port 16 includes a checkvalve barrel 36, ball 39 and spring 40 which collectively provide acheck valve function to allow fluid to flow into valve 100 through port16 but not outward through port 16. The housing of syringe 100 alsoincludes a main cylindrical section 18 and a secondary section 20, and apiston 102 translates axially through section 18 in response to pressureand fluid flow within valve 100.

Unlike the embodiment of FIGS. 1A-1D, however, there is no plunger 26extending from piston 102; rather, piston 102 freely moves withinhousing section 18 solely in response to fluid pressure experiencedinside of valve 100. Instead of a plunger, piston 102 includes anintegral rearward section which extends rearwardly through housingsection 20 and terminates in a bulb 104.

In the embodiment illustrated in FIGS. 2A-2B, piston 102 and bulb 104,and the connecting elastic element 106, are a single, integral element,formed of a flexible material that can stretch resiliently to a greatextent, such as silicon rubber. Connecting elastic element 106 providesa resilient force tending to move piston 102 rearwardly, as discussedbelow. To achieve this, bulb 104 is held against four ribs 107 (see FIG.2C), positioned within housing section 20 in a manner which engages bulb104 and prevents bulb 104 from moving forwardly toward housing section18.

The forward end of housing section 18 includes, as before, a conical endcap 44. End cap 44 also includes ridges 46 which, as before, extendinwardly from end cap 44 and prevent piston 102 from engaging fullyagainst end cap 44, such that a small radial gap 47 is left betweenpiston 102 and end cap 44 even when piston 102 is at its fully forwardposition shown in FIG. 2B.

This forwardmost end of housing section 18 is enlarged in diameter, sothat, as best seen in FIG. 2B, when piston 102 reaches its forwardmostposition, the periphery of piston 102 is no longer able to seal againstthe internal surfaces of housing section 18, and therefore fluid is ableto flow around piston 102, through the gap 47 between piston 102 and endcap 44, and out of outlet port 12. So long as fluid flow continues inthis direction, piston 102 will be held against ridges 46 and will notre-engage the periphery of housing section 18. However, if the pressureequalizes and fluid flow discontinues, elastic pressure from elasticelement 106 will pull piston 102 away from the forwardmost end ofhousing section 18, causing the periphery of piston 102 to re-seatagainst the cylindrical walls of housing section 18 and seal any fluidin end cap 44 and outlet port 12 from communication with housing section18.

The rearward end of housing section 18 includes a similar conicalsection. This section includes a circumferential ridge 108 which engagespiston 102 when piston 102 is at its rearwardmost position shown in FIG.2A, thereby sealing piston 102 and ensuring there can be no fluid flowaround piston 102 when in this rearwardmost position.

In use, the simplified limited backflow reflux valve 100 performssimilarly to the valve discussed in FIGS. 1A and 1B, with the exceptionthat there is no provision for manual injection using the valve. Theprocedure will again be discussed in the context of a contrast mediainjection, although other injection procedures could use valve 100 withlike results.

As before, the first step in using the valve is to fill the syringe. Forthis step, a bulk container of contrast media is coupled to inlet port16, and the syringe is coupled to bi-directional port 14. Then, thepower injector is run in reverse to withdraw air and fluid into thesyringe. This motion reduces the pressure inside of housing section 18and 20 in the region rearward of piston 102. This initial pressure dropproduced by reverse operation of the power injector causes piston 102 tomove rearwardly through housing section 18 to the position shown in FIG.2A, at which time piston 102 ceases motion. (As before, valve 100 istypically disposable and may be provided with piston 102 pre-positionedas shown in FIG. 2A.)

Further pressure reduction caused by continued reverse operation of thepower injector will overcome the compression force produced by spring 40and cause ball 39 to withdraw from the outer end of check valve barrel36, causing air and fluid to flow from the bulk contrast media containerinto inlet port 16, through the housing of valve 100, and out ofbi-directional port 14 into the syringe. Thereafter, continued reverseoperation of the power injector will cause contrast media to fill thepower injector syringe.

When the desired amount of contrast media has been drawn through valve100 and into the syringe, the backward motion of the power injector isterminated. At this instant, the pressure inside of valve 100 isequalized, and as a result the compression force of spring 40 forcesball 39 to engage to the outward end of check valve barrel 36, sealinginlet port 16 from the interior of valve 100.

After thus filling the power injector syringe, a length of high pressuretubing, for connection to the catheter, is attached to the outlet port12 of valve 100. The power injector is then run forward to force any airin the syringe into valve 100 and out through the high pressure tubing.During this operation the power injector is typically tilted upwards sothat any air in the power injector syringe moves to the nozzle of thesyringe. Furthermore valve 100 may be tilted upward so that outlet port12 is elevated relative to the remainder of valve 100 so that gravitycauses any air bubbles entrained in valve 100 to move to and out ofoutlet port 12.

As the power injector forces air and contrast media into valve 100through port 14, a positive pressure is produced inside of the valvehousing rearward of piston 102. This positive pressure generates aforward force upon piston 102 urging piston forwardly toward theposition shown in FIG. 2B. Once piston 102 reaches the forwardmostposition shown in FIG. 2B, air and contrast media are able to flowaround piston 102 and into conical end cap 44 and out of outlet port 12into the tubing connected thereto.

After sufficient forward motion of the power injector, all air in thesyringe, valve 100 and tubing can be expelled, so that the system isprepared for use in injection. Accordingly, the tubing at outlet port 12may be connected to the catheter and the catheter inserted into thepatient.

After the catheter has been properly positioned, a large-scale injectionof contrast media may be performed by activating the power injector.Doing so will cause contrast media to flow into valve 100 throughbi-directional port 14, initially translating piston 102 to itsforwardmost position and thereafter forcing fluid flow around piston 102in this position.

At any time during the injection procedure, the physician may wish towithdraw blood through the catheter and into the tubing to check forpatency of the catheter. To do so, the physician operates the powerinjector in reverse, producing a negative pressure inside of thesyringe. Initially, piston 102 will be at the forward end of housingsection 18, and will respond to this negative pressure by movingrearwardly (in the same manner as discussed above with respect toinitial filling of the syringe), drawing blood out of the patient andinto the catheter. When blood becomes visible in the tubing, it can beconfirmed that the catheter is not blocked.

Once piston 102 reaches the rearwardmost position shown in FIG. 2A,further rearward motion of the power injector will draw fluid into valve100 through inlet port 16 in the manner discussed above with respect tofilling the syringe.

Thus, the valve 100 permits a predetermined quantity of fluid (e.g., 2ml) to be withdrawn from the patient by operation of the power injector,without the need for highly accurate operation of the power injector.Furthermore, because piston 102 is tightly sealed to the interior ofhousing section 18 during withdrawal any blood withdrawn from thepatient into valve 100 is contained within valve 100 in the regionforward of piston 102, avoiding contamination of either the powerinjector syringe connected to port 14 or the bulk contrast mediacontainer connected to port 16.

At any time during an injection, it may be discovered that there isinsufficient contrast media remaining in the syringe to complete theprocedure. In such a case, the technician need only operate the syringein reverse, which (after initial withdrawal of a limited volume of bloodinto the catheter) will cause additional contrast media to flow from thebulk container through inlet port 16 and refill the syringe. Thus, thesyringe may be refilled at any time during the procedure, withoutdisconnecting tubing and without risk of contamination of introductionof air.

The preceding illustrates limited backflow reflux valves in which apiston translates axially in a cylindrical housing to permit forwardflow out of outlet port 12 as well as limited reverse flow into outletport 12. However, other structures may be used to perform this function.

For example, FIG. 3A illustrates a valve 110 including a hinged gate 112which rotates within a fluid channel 114 to permit unlimited forwardflow and limited backflow through the channel 114.

As seen in FIGS. 3B-3D, gate 112 rotates or pivots about an axle 116within housing 120 to perform these functions. When fluid is expelledthrough fluid channel 114 in the forward direction, gate 112 pivotscounter-clockwise to its open position shown in FIG. 3C to permit fluidto pass unimpeded.

Whenever the pressure is equalized and fluid flow stops, however, aspring 118 mounted to the axis of rotation causes gate 112 to pivotclockwise to the sealing position shown in FIG. 3B, thus sealing thefluid channel 114.

Thereafter, if reverse fluid flow is induced in channel 114, gate 112will pivot further counterclockwise until it reaches the position shownin FIG. 3A, at which time gate 112 engages the housing, preventingfurther pivoting and preventing further fluid flow. It will be notedthat gate 112 carries a sealing rim 122 which seals against the interiorwalls of the valve housing 120 and prevents fluid flow around gate 112when gate 112 is at or between the positions shown in FIGS. 3A and 3B.

As seen in FIG. 3D, a torsional spring 118, attached to the axle 116 ofgate 112, returns gate 112 to the position shown in FIG. 3B by applyinga counter-clockwise torque to gate 112.

The limited backflow check valve structure shown in FIGS. 3A-3D, or anyother valve structure achieving these functions, could therefore besubstituted for the piston 102 and main cylindrical housing section 18in the embodiment of the invention shown in FIG. 2A-2B and achievesimilar results.

While the present invention has been illustrated by a description ofvarious embodiments and while these embodiments have been described inconsiderable detail, it is not the intention of the applicant torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. For example, any one of the valve structuresdescribed above could be integrally manufactured with a bulk containerof contrast media, or a disposable syringe, or both, simplifyingassembly and reducing cost. The various functional elements of the valvecould be incorporated in a single housing, as shown in the Figs., or inseparate housings interconnected by tubing. Furthermore, a cupped valvestructure could be used in the simplified valve of FIGS. 2A-2B, thuspermitting fluid flow around the piston in the manner discussed abovewith reference to FIGS. 1A-1B without necessitating the inclusion of anenlarged region in the main cylindrical housing section 18 (althoughsuch an approach might require manufacture of a two-piece piston such asis shown in FIGS. 1A-1B). Moreover, other plunger locking structurescould be used in place of those illustrated in FIGS. 1A and 1B, forexample a friction-engagement lock in place of a toothed lock. Also, thevalve may be supplied pre-filled with contrast to simplify theprocedures for initial connection and use of the valve. The invention inits broader aspects is therefore not limited to the specific details,representative apparatus and method, and illustrative example shown anddescribed. Accordingly, departures may be made from such details withoutdeparting from the spirit or scope of applicant's general inventiveconcept.

What is claimed is:
 1. A method of injecting fluid into a patient, comprising the steps of:providing a limited backflow reflux valve comprisinga housing, an inlet port in said housing, an outlet port in said housing, a bi-directional port in said housing, a first check valve permitting fluid flow only into said limited backflow reflux valve housing through said inlet port, and a second check valve permitting fluid flow from said limited backflow reflux valve housing through said outlet port, and permitting only a predetermined limited volume of fluid to backflow through said outlet port and into said limited backflow reflux valve housing, and preventing any further backflow through said outlet port into said limited backflow reflux valve housing beyond said limited volume, inserting a catheter into a patient and coupling said catheter to said outlet port, coupling a bulk container of said fluid to said inlet port, coupling a syringe to said bi-directional port, driving a piston in said syringe forwardly to force said fluid from said syringe and into said catheter through said limited backflow reflux valve housing, and driving said piston in reverse in said syringe to initially extravasate said predetermined limited volume of fluid from said catheter into said limited backflow reflux valve housing, and thereafter draw fluid from said bulk container into said syringe, said driving steps being performed alternately without disconnection or reconnection of said syringe, catheter or bulk container from said limited backflow reflux valve.
 2. The method of claim 1 whereinsaid limited backflow reflux valve is provided with a cylindrical housing, a piston having a circular periphery fitted in said cylindrical housing for translation through said cylindrical housing during forward and reverse flow of fluid through said outlet port to form said second check valve, and a plunger attached to said piston and extending externally of said cylindrical housing to permit manual translation of said piston through said cylindrical housing to manually inject fluid out of said outlet port, and said method further comprises the step of manually translating said piston using said plunger to manually inject quantities of fluid out of said outlet port and into said patient.
 3. The method of claim 2 whereinsaid limited backflow reflux valve is provided with a lock mounted externally to said housing and movable to a first position to permit motion of said plunger within said housing and to a second position to prevent motion of said plunger within said housing, said method further comprises the step of moving said lock to said first position prior to manually injecting fluid into said patient, and the step of moving said lock to said second position prior to driving said piston in said syringe.
 4. A contrast media supply system for use with a powered contrast media injector comprising:a bulk container of said contrast media, a limited backflow reflux valve comprising: a housing, an inlet port in said housing attached to said bulk container of fluid, an outlet port in said housing for attachment to a catheter, a bi-directional port in said housing for attachment to a syringe, a first check valve permitting fluid flow only from said bulk container into said limited backflow reflux valve housing through said inlet port, and a second check valve permitting fluid flow from said limited backflow reflux valve housing through said outlet port into said catheter, and permitting only a predetermined limited volume of fluid to backflow from said syringe through said outlet port and into said limited backflow reflux valve housing, and preventing any further backflow through said outlet port into said limited backflow reflux valve housing beyond said limited volume, whereby said powered injector may be operated forwardly to drive fluid from said syringe and into said catheter through said limited backflow reflux valve, and said power injector may be operated in reverse to initially extravasate fluid from said catheter into said limited backflow reflux valve housing and thereafter draw fluid from said bulk container into said syringe, such that fluid may be injected into said patient and said syringe may be subsequently refilled without disconnection or reconnection of said syringe, catheter or bulk container.
 5. A fluid injection system for injecting fluid comprising:a power injector having mounted thereon a syringe for holding and pressurizing said fluid, a catheter for insertion into said patient for delivery of said fluid to said patient, a bulk container of said fluid, a limited backflow reflux valve comprising: a housing, an inlet port in said housing attached to said bulk container of fluid, an outlet port in said housing attached to said catheter, a bi-directional port in said housing coupled to said syringe, a first check valve permitting fluid flow only from said bulk container into said limited backflow reflux valve housing through said inlet port, and a second check valve permitting fluid flow from said limited backflow reflux valve housing through said outlet port into said catheter, and permitting only a predetermined limited volume of fluid to backflow from said syringe through said outlet port and into said limited backflow valve housing, and preventing any further backflow through said outlet port into said limited backflow reflux valve housing beyond said limited volume, whereby said power injector may be operated forwardly to drive fluid from said syringe and into said catheter through said limited backflow reflux valve, and said power injector may be operated in reverse to initially extravasate fluid from said catheter into said limited backflow reflux valve and thereafter draw fluid from said bulk container into said syringe, such that fluid may be injected into said patient and said syringe may be subsequently refilled without disconnection or reconnection of said syringe, catheter or bulk container. 